Certain diseases of the respiratory tract are known to respond to treatment by the direct application of therapeutic agents. As these agents are most readily available in dry powdered form, their application is most conveniently accomplished by inhaling the powdered material through the nose or mouth. Alternatively, the drug in this form may be used for treatment of diseases other than those of the respiratory system. When the drug is deposited on the very large surface areas of the respiratory tract, it may be very rapidly absorbed into the blood stream; hence, this method of application may take the place of administration by injection, tablet, or other conventional means.
Several inhalation devices useful for dispensing this powder form of medicament are known in the prior art. For example, in U.S. Pat. Nos. 3,507,277; 3,518,992; 3,635,219; 3,795,244; and 3,807,400, inhalation devices are disclosed having means for piercing of a capsule containing a powdered medicament, which upon inhalation is drawn out of the pierced capsule and into the user's mouth and thus, into the user's lungs and respiratory system. Several of these patents disclose propeller means, which upon inhalation aid in dispensing the powder out of the capsule, so that it is not necessary to rely solely on the inhaled air to suction powder from the capsule. For example, in U.S. Pat. No. 2,517,482, issued to Hall, a device is disclosed having a powder-containing capsule, which is pierced by manual depression of a piercing pin by the user. U.S. Pat. No. 3,831,606 discloses an inhalation device having multiple piercing pins, propeller means, and a self-contained power source for operating the propeller means via external manual manipulation, so that upon inhalation the propeller means aids in dispensing the powder into the stream of inhaled air. See also U.S. Pat. No. 5,458,135.
The above description of the prior art is taken largely from U.S. Pat. No. 3,948,264 to Wilke et al, who disclose a device for facilitating inhalation of a powdered medication. A capsule piercing structure is provided, which upon rotation puts one or more holes in the capsule, which contains medication, so that upon vibration of the capsule by an electro-mechanical vibrator, the powdered drug may be released from the capsule. The electromechanical vibrator includes, at its innermost end, a vibrating plunger rod that is connected to a mechanical solenoid buzzer for energizing the rod to vibrate. The buzzer is powered by a high-energy electric cell and is activated by an external button switch. Moreover, as noted above, in Wilke et al.'s disclosed device, vibration of the powder is activated by depressing a push button. This can be difficult and painful for some users (e.g., patients suffering from extreme arthritis). Finally, in order to use Wilke et al.'s disclosed inhaler most efficaciously, the user must depress the vibration-actuating push button at precisely the same time that the user begins inhalation. This can also be difficult for some users (e.g., very young patients, patients suffering from neuromuscular disorders, etc.).
The prior art, such as described above, is dominated by inhaler devices that are activated by some mechanical means of activation, e.g., airflow sensors that include: flapper valves, turbine valves, swirl generators, vortex measurement devices, hot wire, direct pressure drop, ultra sonic, Doppler shift measurement, etc.
In our prior U.S. Pat. No. 6,152,130, issued Nov. 28, 2000, we provide an inhalation device with a fluid sensor to activate and control various components of the device. The fluid sensor includes an acoustic element, such as a microphone, positioned within the inhalation device to detect fluid within the device and output signals representative of the frequency and/or amplitude of the fluid. These signals control and activate an electrostatic plate and/or a high frequency vibrator. This inhalation device provided improved utilization of mediation by ensuring that the full (proper) dosage of the medicament is released when the patient breathes. However, this acoustic sensor flow does not have the ability to detect the direction of the flow of air. If the sensor detects a flow of air while user is exhaling, the medicament could be released at the wrong time and the patient would not receive the full dose.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.